1. Field of the Invention
The present invention relates to a medical manipulator used for laparoscopic surgery, for example, and in particular to a manipulator joint displacement detection mechanism for detecting the degree of displacement of a joint of a manipulator.
2. Description of the Related Art
A medical manipulator is used for laparoscopic or thoracoscopic surgery. The medical manipulator is provided with a joint in the distal end portion. A joint is provided with a clutching unit equipped with a surgical instrument such as a pair of forceps. The medical manipulator transmits power of a driving source such as a motor to a joint. A member to transmit power (power transmission member) is a linear member such as a wire. A power transmission member is provided movably along a guide member inserted in the medical manipulator. A joint is displaced by the transmitted power. A clutching unit changes an angle of rotation of the pair of forceps, for example, according to displacement of a joint.
In laparoscopic or thoracoscopic surgery, a patient's abdomen is punctured, and a jig called a trocar is inserted into the puncture. A medical manipulator equipped with a surgical instrument at the distal end is inserted into the patient's abdomen through the insertion hole of the trocar. In this state, the surgical instrument of the medical manipulator is operated, and surgery is performed.
The aperture of an insertion hole of a trocar used at present is less than 10 mm in diameter. The aperture of the medical manipulator inserted into the trocar must be smaller than the aperture of the trocar. A typical medical manipulator is used in the Intuitive Surgical Corporation's Da Vinci system. The medical manipulator used in this system is formed to have a diameter of 10 mm or less, and a length of 300 mm or greater, in which a clutching unit equipped with a surgical instrument such as a pair of forceps is operated with multiple degrees of freedom.
A power transmission member of the medical manipulator uses a linear member such as a wire. Even the manipulator of the Da Vinci system uses a power transmission member such as a wire. The power transmission member is formed to have a diameter of less than 0.5 mm, for example, to transmit power in a limited space of diameter less than 10 mm.
A manipulator using a linear power transmission member having a small diameter is disclosed in U.S. Pat. No. 5,807,377, for example. This patent application discloses a technique of detecting displacement of a joint by a potentiometer or encoder placed close to a driving source such as a motor.